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NPS62-89-023
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NAVAL POSTGRADUATE SCHOOLMonterey, California
TECHNICAL REPORT
Image Enhancement Software forUnderwater Recovery Operations
-User's Manual
William J. PartridgeCharles WV. Therrieni
16 June 1989
Approved for puiblic release; distribution unlimited.
Prepared for: Naval Undersea Weapons Engineering StationKeyport, WA 98345
89 9a 2.6 1 ;5
NAVAL POSTGRADUATE SCHOOLMonterey, California
Rear Admiral R. 'A. Uest, Jr. Dr. Harrison Shull
Superinte2ndent Provost
RQ-roduction of all or part of this report is authorized.
This report was prepared in conjunction with research conducted forNuv, Undersea Weapons Engineering Station and funded by the NavalPostgraduate School.
Willia . artrdeMajor, U. S. Army
Charles W. Therrien
ProfessorDepartment of Electrical and
Computer Engineering
Reviewed by:
JOH'! ' POWERS GORDON E. SCHACHERChairman, Department of Dean. Science and Engineering
Electrical and Computer Engineering
REPORT DOCUMENTATION PAGE
a :t C~ n ; 'TR C \z MA'RK:IGS
UNCLASSIFIED.d -S.C . CASD . ' T 0'. A.A , ,A 7 OF REPORT
, * C,
NO QRCAN ZA-,ON REPCRT N ),BER(S,
NPS 62-89-023
. ,01, '_ - . CE P, 'a N-E V ,ONORNG ORGANIZAT:ON
Naval Postgraduate School (It apphcable) Naval Undersea Weapons Engineering Station
6 " ,-' C 7) sr. re a (; Z C c 7 ,DDR-SS Cftj. State. and ZIPCode)
Monterey, CA 93943 Keyport, WA 98345
; : C- S'.'B0. 9 PROCUREVEN NS7RUM%,EN.T iDENTti;CA;ON IUV2;
(K' appltcao'e)
Naval Postgraduate School O&MN, Direct Funding:. ='1- :- .. : & :: a-a . , .. '-j" C, ') E C- :_, :.. ,_ ,";" "
POGAM O)ECT -ASK )N,TMontercy, CA 93943 EEMENT NO 1NO NO ACCESS:ON NO
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Image Enhancement Software for Underwater Recovery Operations-User's manual
William J. Partridge, Charles W. Therrien
3a E- CC2 4 DAE 0F REPORT (Year. Month, Day) I's PAGE COr,,NT6J _ o-j/9. 16 June 1989 I 20
* -: -, ,6' " 5,ECT TERMS (Continue on reverse 'i necessary and identif'y by blocK number)_Di I c video image enhancement, image processing, underwater
recovery, underwater viewing
jA: - C r rji e rce-sC t n,:crssao, arc cien'It) b biock number)
This report describes software for performing image enhancement on live or recordedvideo images. The software was developed for operational use during underwater recoveryoperations at the Naval Undersea Warfare Engineering Station. The image processing isperformed on an IBM-PC/AT compatible computer equipped with hardware to digitize anddisplay video images. The software provides the capability to provide contrast
enhancement and other similar functions in real time through hardware lookup tables,to automatically perform histogram equalization, to capture one or more frames andaverage them or apply one of several different processing algorithms to a capturedframe. The report is in the form of a user manual for the software and includes guided
tutorial and reference sections. A "Digital :mage Processing Primer' in the appendixserves to explain the principle concepts that are used in the image processing.
TU. A. t- : A- CT 21 ABSTRACT SECURiTY CLASSFCATION. D J\.'D [ SAME AS RPT E DTIC USERS
S":,','- C.S - .j",v --. _- 22b TELEPHONE (incluoe Area Code) ac OFFICE SYMBOL
Charles V. Therrien
DD FORM 1473, a;- AF P 0 t on may oe Used Unto .xna ted SECURITY CLASSIF'CATION OF THIS PAGEA,: .,ther ed~tions are obsolete 0 U.S. Go., me nt ., office ,906-606-2o .
A BST R ACT
Thlis report describce, software for perf'orming image enhancement on live or recordedvideo imacs. 'I'ie software was developed for operational use during underwater recov-
cry operationis aIt the Naval Unders.ea WVarfaire E~ngineering Station. The imiage procss-
ing, i, perfeCrmled Onl anl IBM-PC ATF compatible computer equipped with hardware to
dliwie an d dis;play videco imacges. The software provides the capability to provide con-
trast enhancement and other simidlar functions in real time through hardware lookup
table, to autonmtically perform histogram equalization, to capture one or more frames
and avecrage theml, or apply one of sev eral different processing algorithms to a captured
frlame-I. T*he report is in the f'orm of a user manual For the software and IilIudes OUIded
tutorial aind diecesec:tions A 'I-iital i mac Processing Primer' in the appendix
ere to explain the principle concepts that are us ed in the image proce-ssing.
T
TABLE OF CONTENTS
A. G ENt 1E L.. L ................................................ I
B. FQL.IPM [NT R[QUIRLD .................................... 1
C. SIMPLIE SETUP .............................................. I
1, Getting the Board Ready .. .................................. I
2. Installing the B oard ..... ... ....... .. .... .. .... ... ....... .. 2
3. C able Installation .... .. .......... ............ ........... .. 2
4. Running the 'iagnostics . . ...................................
I). LETS T R Y 1i O U T . .........................................
1. Load the Program
2. L ive A ctio n .............................................
3. lake a Snapsh ot .... ........................ .... ..........3
4. 1 ake Two Snapshots . ...................................... 3
5 . A ll B la ck ...............................................3. .. W hite ...................... ......... ...... ..... .. ...3
Put Your Snapshot in the Photo Album ........................ 4
S. Open the ..\lhu to See Your Snapshot .......................... 49. Sim ple Process ne. ......................................... 4
it). I listogram i Lqualization .......... ........................ 5
I . f3ef',re and A fter ...... ...................................5
12. M odifying the Lookup Table ................................ 6
13. )raw Your Own Lookup Table .............................. 6
14. Storing and Retrievinm Your -avorite Lookup Tables ............. 7
15. Piggyback lookup Tables ..................................
10 . Z o o m .................................................7
17. L n zo o m ...............................................8
I8. Sharpen . ............................................... S
19. Low Pass Filter ...........................................
2). \n Edge D etector ........................................ 8
21. I m age A veraging ......................................... 8
. Q I_J(K R JI- LR .N CI LIST . . .................................. S
1. A for sel.cct m em ......................................... 9
2. B for select mern B. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 9
I. (- Ifori display Ae A.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ...
4. 1 ) fo r displax inei B .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 9
5. F fo r grab .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. . .. .. 9
G ' fr -clear((- ). .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ... 9
S. I11 for sclear 25 5). .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 9
9. 1 to store im1age9C.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ... 9
D ). Ito read inMEC'. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 911 . Kto change2 setuIp. .. .. .. .. .. .. .. . . .. .. .. .. .. .. .. .. .. .. ... 9
12. L For analy sis .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . 9
C. h1 histoerarnil.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ... 1
J. e = cq ualize .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .1
.p= loglut..... .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . ..
h. a abslut. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . ..
1. = freeze .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . ..
k. s =stop. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . . . .
\1 N to stoic lookup table. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 2
14. Nto read lookUp table .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 12
15. ()to select output lookup tab-le .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 12
16(. 1) to select in1put lookup table. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 12
17-1. Q) for zooni. .. .. .. .. . .. . .. . .. .. . .. . .. . .. .. . .. . .. . .. .. . .. 12
IS. R for unzoom. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 12
19Q. S for sharpen .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ... 12
21). T f'or low pas.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 1 2
21. Vor edge detector. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ... .. 12
22. V for image average. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ... 12
2 3. W for frarnegrabber off and exit programn.. .. .. .. .. .. .. .. .. .. .. 12
A TFNIIX A.- DIGITA~L IMAGE PROCESSING PRIMELR. .. .. .. .. .. .. .. I
A . GNRN EARL . ............................................... 13
B. IIIL1 )Il AL INIA G E ..................................... 13
C . T ill: HIISTO G RA M ......................................... 13
D . '111L LO O K U P TA BLI ....... ............................... 14
II:\L I) STRIBUTION LIST .................................... 17
iL"
A. GENERAL
Ihe "Menu" software package is a menu driven program which provides real time
continuous video image processing using lookup table modification techniques. It also
provides linited non-real time single frame enhancement capability. Control of the
roul:nes in "Menu" varies from manual (requiring operator input to make an adjust-
ment) to automatic or "hands-off' operation. The processing routines were chosen to
provide iimum effectiveness in situations where the images' pixel values are limited
to a relatively small region of the total gray scale range. Typically this would include
images of objects which have actual small variations in shading or those whose contrast
has been reduced by obscuration or dim lighting.
B. EQUIPMENT REQUIRED
'Ihe following equipment is required to use the "Menu" program:
" IBI Personal Computer AT, XF. or PCI or 100' o compatibles with ExtendedGraphics Adaptor card and monitor.
* Imagin., Technology PCVISIONplus Frame Grabber card with standard cable.2(NO IL: Ilhe older model PCVISION F'rame Grabber will not work.)
* Analog video monitor (such as SONY Trinitron 3 Model 1271Q).
• Video source (camera or video tape player).
C. SIMPLE SETUP
-lie 1CVStONolus Frame Grabber User's Manual provides all the information
required to place the Frame Grabber into operation. Itee is a much condensed version
of that procedure with some helpful hints to ease the way.
1. Getting the Board Ready
Figure 2-1 on page 2-' of the Frame Grabber Manual shows the jumper lo-
cations on the board and Table 2-1 on page 2-3 tells how they are configured from the
factory. There are three position functions to be concerned with:
* Since an EGA card is needed to run "Menu" the memory base address must bechanged on the Frame Grabber board. Address DOOO is recommended since thisis the def'ault value in the software. To change to address DOl(), simply insert ajumper at location JS. If other than DOOO is chosen it should be noted for entryeach time "Menu is run.
I Trademark of IBM.
2 lradcmiart of lmiaing Technology Inc.
3 -1ra dnark of SONY
"'Menu" has a default register base address of 100. To change the FrameGrabberboard insert a jumper at location JIll. Again. if 100 is not used, the chosen valuewill have to be entered each time "Menu" is run.
If an AT host is being used a jumper is required at location J20. If an XT or PCis being used no jumper should be installed at J20.
2. Installing the Board
Pages 3-1 through 3-3 of the FrameGrabber Manual provide a detailed de-
scription for installing the board. A summary is as follows:
* Turn off and unplug the computer and periphials.
* Remove the cover.
P Place the board in any open slot where it fits and install screws.
* Reinstall cover.
* Plug in and turn on computer.
3. Cable Installation
Page 3-5 ofthe Frame Grabber Manual shows how to connect the cable. I lere's
the bottom line:
* Plug the rectangular female connector on the cable into the top connectorprotruding from the board.
• Connect the whtc laheled BNC connector to the video source output.
• Connect the green labeled BNC connector to the 'line' input (not the 'green' inputof the red, green, blue connections).
* Do not connect the red- or blue-labeled cables.
4. Running the Diagnostics.
Pace 3-10 of the Frame Grabber Manual describes the procedure for running1
the diagnostic software included with the Frame Grabber. Since the factorv configura-
tion has been changed as described above, the command < configure> will have to be
entered followed by the register base address (100) and the memory base address
(D0000). The diagnostics take several minutes to run so be patient. As stated in the
manual, system memory or other devices mapped into the same memory space or regis-
ter addresses will cause some tests to fail.
D. LET'S TRY IT OUT
This is an introduction to the "Menu" program. It let's you walk through some of
the features of the program; sort of a hands-on familiarization. If you are not familiar
with some of the concepts described in this section, or with digital image processing in
2
general, you should probably lhve a look at the Primer which is included in this docu-
ment I an appendix. It e\plain, the neccessarv ideas in just a few pages.
Now tur1n on \ our source (camra or VCR and video monitor to let them warm up.
On %our computer go to the directory where you want to keep the program and copy
menu.e\e there.
1. Load the Program
To get started simply type the word 'menu' followed by <enter>. No <en-
ter - is needed for any selection from here on out unless otherwise noted. The menu
should now he display ed on the computer monitor. If ou are not using the memory
ba,e address 11)(000 and register base address (100) as described in paragraph C above,
ht K to chan,:e setup and follow the instructions on your monitor.
2. Lke Action
Ylen;u selcktion 'I5" provides continuous acquisition and display of the incoming
real imc \ideo imaces. lit '_' and you should see live action from ,our camera or VCR.
If"ou're usirig a tape make sure you press the play button first .
3. Take a Snapshot
Now let's freeie the action. I lit 'I' for snap. This acquires and displaxs a single
frame. You should see a stop action snapshot on N our video monitor. lhe image is also
stored now in framezrabber memory A. the default memory chosen when xou started
up.
4. Take Two Snapshots
Now hit I)' for dinplav memory B. Take another snapshot with the '12' key.
The second snapshot is now displayed on the r-onitor and stored in fraime rabber
nlCmeo:v B. Trv going bac:k to memory A (the 'C' key) to make sure the flirst snapshot
is sLll; there. Note that we are using the display memor- keys and not the select memory
kexs to perform these operations. NMore on select memory later when we start storingimages.
5. All Black
Let's erase one of our snapshots. Display memory B (the 'D' key) and then hit
the 'G' key for screenclear(O). This clears the screen and framegrabber memor-y B to
black or intensity level zero.
6. All White
While still in memory B hit the '11' key for screenclear(255). This erases the
screen and memory B to white or intensity level 255. Darker gray shades have lower
inten:ity levels while lighter shades have higher intensity levels.
* 3
7. Put Your Snapshot in the Photo Album
Sax ing an image to disk is analogous to putting your snapshot in a photo al-
bumn. You should still have an image in frame memornv A. If not. use the display nim
A and snap routines to get one. Now hit the 'A' key to select memory A. This selects
memory..\ for data manipulations or storage. For our purposes we have selected theimage data in memory A to store on disk. Now hit the Tl' kev and you will be asked to
enter a:'n image name. Ty'pe a name (e.g. 'image') to store the image on the current disk
and directory or path and name (e.g. 'a: iniage') to store it in a different place. Then
xoul 1 be prompted for a comment. You may give it a label ox simply type 'none' (note
that - enter > is required for each of these inputs). The disk drive selected should make
some noieC and your snapshot is satel' tucked awav in the "photo album" (i.e. the ima2e
ti1e is r:kttcti to the disk.
8. Open the Album to See Your Snapshot
lct', see itthe imace was really saved. First erase both Frame nemories a,
desribcd in paragraph 5 or o above. Then select a memory using 'A or '11. Now hit
tic Jkcx. l',pe the image file name ,Iollowed by < enter>) to read the iitnae Ci1
khk. I he im:tgc should appear on the video monitor. If it does not. display the memory
x Cu sClectCd 'the 'C' or I)' key) and the image will appear.
9. Simple Processing
Now let's process real time video images using some simple lookup table mod-
itiea tion t chniqu , a I lit the L' kev - its called analysis, but reallv it just lets iou see
now " o1r iage i being changed. The graph you see on your computer monitor is the
current lookup table. 'lihe horizontal coordinate represents input pixel values and the
x erticl repreets output values.
()n the top of' the computer monitor screen are the current option, available For
Se ctit,,'. The snap (I-"' aiid grahb (i') options work the same as on the previous menu.
-lrv them' Now try the invlut (I ) option and see how the lookup table chances (the
blue line is the current lookup table and the green is a reference linear lookup table line).
'I hC Cflect on the inuge is just like looking at the negatives o'a photograph, except that
we still haxe lixe action. Now hit the 'L key for linear lookup table. We are back to
unprocessed live images.
Kexs 'P' (logarithmic and 'A' (absolute Nalue) also modify the lookup table.
You can experiment with these functions to see the effect on the real time image and
their clrreopom~din g Iookup taqe shape.
10. Histogram Equalization
Now for the most powerful of our lookup table modification routines. I flit 'E'
for equdliie. Y 4 now are Liven two choices. default and rectangle. This determines
which portion of the image will be used to do the processing. Iost of the time you
will probably use the default mode but let's try rectangle now just for fun. lit 'R' for
rectangle. On the video monitor you will see the live images being displayed with a
rectnle overlaid. Now hit 'Num Lock' en your keyboard. Using the '2', '4', '6', and
'S' keys on the number pad ithe ones with the arrows) you can move the rectangle
around or, the screen. The corner numbers ('1', 3', 7', and'9') are used to change the
size of the rectangle. If your image had a large white or black area in which you were
not interested, it w-oald lessen the impact of the equalization routine on tie area of in-
terest. So you would frame the area of interest with the rectangle. After you have
placd the reiLtanye where you want it. hit S for stop.
Now you have to choose between manual or automatic update. Try manual
Splate first. I lit the NA key. The image will equalize, the new lookup table is plotted.
a 1: h" e action continues using the new lookup table. In this mode, as you notice the
contc:,t, of the im&ge changing you can hit the V" key and equalitation will occur again.
Let, go back now and try the default rectangle parameters. I lit 'C' to change
paramnieters. Now hit 'I)' for default and 'C' For continuous update. You are prompted
for tnnc between updates in seconds. lnter any number 2 through '4. The computer
vill pcrf'rm a new equalization at the interval you specify. Ihis is intended for situ-
at, ion, wh Cre the contents of -he inage are changing often and \ o u dont want to have
to remen'.ber to update. When you have seen enough updatem hir A for stop.
I1. Before and After
Lc Kslok at some histocrams and see whats happening when we equaiic, lit
the 'I V kc', for histograin. Again. you may choose between delault or rectangle to
specify a portion of the image. lt 'D' for default. Now hit tie 1' key for computation
of linear lookup tablo histogram. After the "COMPUTING IIISTOGRAMI- indicator
goes away hit 'NI for computation of modified histogram. W\hen the indicator goes
away this time hit 'D' to display the linear lookup table histogram. This is the infor-
mation used to perform the equalization. The image on the video monitor is the un-
processed version. Now hit 'E' to display the modified histogram. The video image is
enhanced and the "spread out" histomam is displayed. As you toggle back and forth
bctvccn 'I) and Y you can see grar'hically how equalization lets us use the fuli ranje
I I I I
of intensity levels and the corresponding enhancement of contrast on the image. Con.
vinced? I lit the S' key and let's try something else.
12. Modifying the Lookup Table
lilt the 'N' key. Now we'll go again to the number pad with 'Num Lock on.
Usinc the corner keys '1. '3'. '7', and '9') we'll change the slope of the lookup table by
moving the top or bottom of the curve. To shallow out the lookup table use the '9' key
to move the top to the right and the '1' key to move the bottom to the left. Notice that
enhancement to the live images changes as you modify the curve. When you are finished
hit S' to stop and the resulting lookup table is shown. If you were to develop a "fa-vorite' lookup table which you think you might want to use again, there is a way to save
it in the computer. We'll talk about that later.
13. Dras Your O'sn Lookup Table
Now hit 'M' to perform another form of manual lookup table modification.
Well do this by drawing lines. Using the number pad with 'Num Lock' on move the
pointer on the computer monitor by hitting the '2', '4', '6'. and '8' keys. This will move
it one pixel In the direction of the arrows on the keys. The next key clockwise from each
oft!-ese will move it in the same direction ten pixels . (e.g. The '1' key moves the pointer
in the same direction as the '2' key only faster.) When the pointer is at a location where
you want the line to begin hit 'B' for begin line. Then move the pointer to a location
where you want the line to end and hit 'E' for end line. Now hit 'D' to draw the line
and your chance will take effect on your image. You may draw other lines to connect
secrnents and build a whole new lookup table. To get rid of the clutter just hit 'S' and
then reenter the routine b% hitting 'I'.
Now hit P' to pLUt a pointer on the live video image. To move tile pointer use
the number pad keys In the same manner as x ou dId to move the pointer on the com-
puter monitor described above. Notice on your computer monitor that the position of
the pointer and the intensity level are displayed. One possible use of this capability
would be to find the intensity level of an object in the image and use the draw lookup
table rouline to change all pixels with that intensity to another level. Again, if you were
to draw a reall, :, d al' purpose lookup table, you could save it with a routine which
we'll describ I lit 'S' to exit the video monitor pointer routine and 'S' again to exit
the nodify rouuti-e
6
Finally. let's go back to the main Menu to see the lookup table storage selection
routines and try some single frame (Frozen) processing. Type "S' to exit the analysis
function.
14. Storing and Retrieving Your Favorite Lookup Tables
Remember that lookup table N ou designed using the modify routine a while ago?
I lere's how you can save it for future use. I lit the 'M' key. Type in a name (e.g. 'mylut'
or 'a: mniut). hit enter, and the values ire saved. To get it back hit the N" key to read
the lookup table values from disk. Again, type in the file name followed by enter and
your lookup table will take effect.
15. Piggyback Lookup Tables
The framegrabber board has two sets of lookup tables, one as the image is put
into frame menory and one as the image is output to the monitor. Up to this point we
have ov u::ed the output lookup tahie. Now we'll modif\ both sets to achieve a dill
fcrent result. flit the ' key to select the input lookup table. Then go back to the
analysis routine ('L) and do a histogram equalization. Everything still looks the same
as the last time we equalized , including the video image, but this time the computed
values went into the input lookup table. Now exit the equalization and analysis routines
to get back to the main menu. 1-lit the '0' kev to select the output lookup table. Then
go back into analysis. You may now use any of the lookup table modification routines
(e.g. in~lut, abslut, etc.) and you will get a "piggybacked" lookup table effect on the im-
aLe. To cet back to normal, hit 'L' to linearize the output lookup table. Go back to the
main mcnu and select and linearize the input lookup table. Note that when you use this
procedure. alwavs put values derived by equalization into the input lookup table or the
equalization will be based on already modified data.
16. Zoom
Now hit the 'R' key to start the zoom Iflnction. On the video monitor y'ou can
see the rectangle we saw before. Using the number pad with 'Num Lock' on you can
move the rectangle with the '2', '4', '6, and 'S keys in the direction of the arrows on the
keys. The size of this one is fixed at approximately one quarter of the screen, since we
will be expanding the image to four times the original. Move the rectangle to the por-
tion of the imace you wish to zoom in on and hit 'S'. The expanded image is displayed.
Notice that some resolution is lost from the original because we are "zooming" digitally
as opposed to changing the focal length of the camera lens. lit 'M' to get back to the
menu. Now you can process the "zoomed" image using the fixed image processing rou-
tines dcscribed bclow.
7
17. Unzon
To return to a normal image after using the zoom routine and performing any
fixed image processing hit the 'R' key, It is essential that this be done when you are
,iched with a "zoomed' image or the zoom parameters will interfere with other rou-
tines.
18. Sharpen
Snap anl image by hitting the 'F' key or by using the zoom routine (the R' key).
Then hit 'S' to sharpen it. If you watch closely you can see the sharpening occurring
on the displayed image.
19. Low Pass Filter
Snap or zoom another image and then hit 'T' to call the low pass filter routine.
This function is designed to remove high frequency noise from a fixed image. Again.
looking closely you can see the change occurring.
20. An Edge Detector
One more time. snap or zoom an image. This time hit the 'U' key to perform
a Sobel Edgc Iiter. Note the interesting display of the image's edges on the video
monitor.21. Image Averaging
Ilit the '" key. Then enter the number of image frames you want to average
together. 'his number may be limited by the amount of disk space you have available
(2 is a good number to start with). When the averiige image is displayed you should
notice that objects wilich passed across the field o1 view during the operation have f'aded
away. Tihe more frames you average, the less visible these objects will become. Image
averaging is very effective at elininating transient noise, but requires a stable platform
for the source.
To exit the program hit the V' key.
E. QUICK REFERENCE LIST
This list presents the program's options in the order they appear with a brief de-
scription of their output.
• i nn a ua IN U nu l 8
1. A for select mere A
Selects framegrabber memory A for storing or reading an image to from disk.
2. B for select niem B
Selects Framegrabber memory B for storing or reading an image to from disk.
3. C for display meni A
Selects Framegrabber memory A for acquisition of image from camera and dis-
plays memory A on the monitor.
4. D for display mem B
Selects framegrabber memory B for acquisition of image from camera and dis-
plays memor B on the monitor.
5. E for grab
Continuously acquires image frames from source and displays on video monitor.
Uses fiamegrabber memory designated by 'display mer' functioa.
6. F for snap
Acquires a singlc frame from source and displays it on the video monitor. Uses
framegrabber memorv designated by 'display mem' function.
7. G for sclear(0)
Clears screen and memory to intensity level O.
8. H for sclear(255)
Clears screen and memory to intensitv level 255.
9. 1 to store image
Stores contents of selected memory to disk. Prompts input of filename (includ-
ing path if desiredJ) and conmnnt.
10. J to read image
Reads image from disk file to selected framegrabber memory. Prompts input
of filename (including path if desired).
11. K to change setup
Allows change of software memory base address and register base address. On
screen instructions and example inputs provided.
12. L for analsis
Dispfays lookup tables and histograms. Performs equalization and lookup table
modification routines. Options as follows:
a. m = modlut
Modifies lookup table by drawing lines. Places pointer on video monitor.
Move pointer to desired start point and end point using 'Num Lock' on and number pad
9
keys '2', '4*. '6'. and 'S' for down, left. up. and right respectively. Use keys 1, '7', '9',
and'3' for faster movement down, left, up, and right respectively./I, b = beginllre. .Maii ks beimiing ufiiill,.
'2/ e = en/line. Marks end of line.
,3) d= drawline. Draws line and enters new values into lookup table.
(4) p = pointer. Places pointer on video monitor. Gives pointer location
and pixel intensity level of that location on computer monitor. Use same method to
move pointer as for line drawing routine above.15, s=stop. Exit lookup table modify routine.
b. n = mnod2 tur
Changes slope of existing lookup table and implements results. With 'Num
Lock' on use number pad keys '1' and '3' to move bottom of curve left and right re-
spectively. Use '7' and '9' keys to move top of curve left and right respectively. I lit 's'
to exit this routine.
c. It = his togramn
Computes and displays histograms for images processed with linear arid
modified lookup tables. Snaps images before and after processing and allows for com-
parison.
I: dl= default. Selects default portion of image for histogram computa-
tion (approximately 90 o of image).
12) r= rectangle. Displays rectangle superimposed on image on video
monitor. Change portion of image used for histogram computation by altering rectangle
size and location. With 'Num Lock' on, use number pad keys "2', '4'. '6'. and 'S' to miov e
rectangle down, left. right. and up respectively. Use '' and '3' ke's to increase and
decrease height. Use '7' and 9' keys to increase and decrease width. lit 's' to exit rec-
tangle routine.
(3,/ 1= corn linl; r. Computes histogram of image processed by linear
LUT. Displays "COMPUTING HISTOGRAM" message until done.
:4) n = coin modhist. Computes histogram of image processed by
modified LUT. Displays "COMPUTING HISTOGRAM" message until done.
(5) d=dis linhist. Displays histogram computed above using image
processed by linear lookup table. Unprocessed image shown on video monitor.
16/ e= dis nodhist. Displays histogram computed above using image
processed by modified lookup table. Processed image shown on video monitor.
s = siop. Exit histogram routine.
10
d. v = equalize
Pcri,ns histoEranI eq Uali/ation with update on commnand or automatically
at specified intervals I p,.s resulting lookup table after each update.
i id=a1:1u/il. Selects default portion of image to use for equalization
(approxinately 90-. of image .
2 ,= rccitigle. Allows use of rectangle to specify portion of image to
be used a. described in hiistogram rectangle routine above (paragraph 12.c.(2)).
3 c= c,,ltiu,,us update. Selects automatic update of lookup table at
specified intervals. Prompts for desired interval. I lit 's to exit equalization routine from
this mode.
.4 = tuala! updae . Selects lookup table update on command.
(a) u =update- Performs new equalization and updates lookup
table.
b c = changeparam- Returns to default rectangle portion of
iMeC options for changing parameters.
c) f= freezeframe- Acquires and displays a single frame (snap).
d) .,r=rab- Continuous acquisition and display of imagefl-ames.
e) s stop- Exit equalization routine from this mode.
e. 1= linlut
Sets lookup table to linear values. Results in unprocessed image.: i= in 'lut
Set, l0c,,kup table to inverse values. lroduccs a necative imaCe..'. /7 = lJ-ltt
Scts lookup table to logarithmic values. Increases image brightness.
h. a ab.rlut
Inverses intensity levels greater than 127. Reduces image brightness.
i. rab
Continuous aquisition and display of image frames.
j. f=f-eeze
Aquisition and display of a single frame (snap).
k. = .top
Exit ana l\ sis routine.
11
13. NI to store lookup table
Stores contents of selected lookup table to disk. Prompts input of filename
(including path if desired).
14. N to read lookup tableReads lookup table values from disk to lookup table they were stored from.
Prompts input of filename (including path if desired).
15. 0 to select output lookup tableSelects the output lookup table to perform modifications on and for display in
the analysis routine. When used in conjunction with P' (select input lookup table) al-
lows for process:ng through two modified lookup tables.
16. P to select input lookup table
Selects the input lookup table to perform modifications on and for display in the
analvsis routine. When used in conjunction with '0' (select output lookup table) allows
for processing through two modified lookup tables.
17. Q for zoom
Enlarges chosen area of image. Provides moveable rectangle to select area for
zoom. With "Num Lock" on use number pad keys '2', '4', '6'. and '8' to move rectangle
down. left, right, and up respectively. Ilit 'z' to stop rectangle and fix, zoom image. Ilit
'mi to return to main menu.
18. R for unzoom
Returns image to normal state.
19. S for sharpen
Sharpens fixed image using a high pass filter. May be used on zoomed image.
20. T for Io'i pass
Performs a low pass filter operation on a fixed image. Reduces high frequency
noise. Blurs the image. May be used on zoomed image.
21. U for edge detectorPerforms Sobel edge detector operation on a fixed image. Displays detected
edges. May be used on zoomed image.
22. V for image average
Averages specified number of image frames and displays results. Prompts input
of number of frames to average.
23. W for framegrabber off and exit programTerminates program.
12
APPENDIX A. DIGITAL IMAGE PROCESSING PRIMER
A. GENERALThis appendix provides the reader with some background on the basics of digital
image processing. It describes the makeup of a digital image, including the concept of
pixels and how gray level shading is accomplished. It also describes the histogram, a
basic tool in the analysis of a digital image. Finally it introduces the lookup table, which
is the primary image processing tool used in the "Menu" program.
B. THE DIGITAL IMAGE
Think about a black and white photograph. Suppose you were to overlay a grid on
it which is 512 squares across by 512 squares down. The picture is divided into 512 x
512 = 262,144 tiny squares. Each square is called a pixel. Now look at an individual
pixel to see what color it is. If it is black it will be assigned the lowest number, intensity
level 0. If'it is white it will be assigned the highest number, intensity level 255. Different
shades of gray will be assigned intensity levels between 0 and 255, with lower numbers
for darker grays and higher numbers for lighter grays. Once the image has been broken
up into pixels and each pixel has been assigned an intensity level, it is said to be digitized.
It's intensity levels are then stored in order somewhere in the computer. In the case of
the framegrabber it is placed into frame memory (either A or B) for processing and or
passing on to the monitor.
C. THE HISTOGRAM
Now Ict's look at our digitized image and count how many black pixels (intensity
level 0) are in it. Then we'll count the dark, dark grays (intensity level 1), the dark grays
(intensity level 2), and so on, all the way up to the whites (intensity level 255). When
we are finished we will have analyzed the image with respect to gray level content. A
plot of this gray levcl content is called a histogram. A histogram is normally plotted as
a bar graph, with the intensit, levels (0 to 255) plotted across the bottom, and the
number of pixels which have each intensity plotted as a v,:rtical bar (see figure 1). The
"Menu" program has a routine which allows you to compute and display the histogram
of an image. The histogram values are also used in an important lookup table modifi-
cation technique, the histogram equalization.
13
4
2
0 l00 z00
Figure 1. Example of flistogramn
D. THE LOOKUP TABLE
A lookup table provides a way to change all pixels of a particular intensity level to
another intensity level. The table has 256 possible input values (one for each possible
gray level in the original image) and a corresponding output value for each input.
Lookup tables are normally plotted graphically with the input values across the hori-
zontal axis and the corresponding output values on the vertical axis. A lookup table
whose output values are the same as it's input values will not change the image and is
called a linear lookup table. It plots as a straight line from the lower left corner to the
upper right corner of the lookup table graph as shown in figure 2.
An inverse lookup table changes black pixels to white, white pixels to black, and in
between values to their difference from 255. The image processed through the inverse
lookup table looks like a photographic negative. We refer to it as a "negative" image.
lhe inverse lookup table plots as a straight line from the upper left corner to the lower
right corner of the graph as shown in figure 3.
A lookup table stretch is performed by setting low and/or high valued intensity lev-
els to zero and stretching the reduced input range of values to a full scale output range.
14
OUTPUT
288
10-
ii I II
S 188 280 INPUT
Figure 2. A Linear Lookup Table
1 he resulting graph is a straight line with a steeper slope than our original linear lookup
table (see figure 4) and the image will have overall enhanced contrast; the steeper the
slope the greater the contrast, but for a smaller range of input values.
A more powerful, nonlinear form of stretching the lookup table is the histogram
equalization technique. It performs localized stretching of the lookup table by detecting
the areas of the histogram which have few or no pixel counts and using them to stretch
high pixel count areas across. I listogram equalization is a very efficient means of con-
trast enhancement. The "Menu" program is based primarily on lookup table modifica-
tion techniques and provides the user with the capability to modify the lookup table in
many different ways including those described above.
. 15
OUTPUT
a180 288 INPUT
Figure 3. An Inverse Lookup Table
OUTPUT
zoo-
too-
8 16la 286 INPUT
Figure 4. A Lookup Table Stretch
16
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